NEW YORK (Fortune) -- A tiny software company called meebo Wednesday opened a new channel of communication on the Web. Now, if you have a Web page your visitors can talk to you using instant messaging, even if you're away from your home computer. (That includes all you MySpace users.)

If this doesn't sound interesting, you are probably over the age of 25. The founders of meebo are, but just barely.

"Like Hotmail put e-mail into the Web, we put IM into the Web," says meebo CEO Seth Sternberg, who is 28.

meebo got its start when its three founders, Sternberg and Elaine Wherry, 27, and Sandy Jen, 25, were all meeting repeatedly at one another's houses in Silicon Valley trying to come up with ideas for a consumer Web company.

As a company history on meebo.com explains: "Sandy kept having this problem where she couldn't easily IM her friends from Seth's and Elaine's houses. Hence, meebo!"

That was meebo's first innovation - a very efficient and rapid Web-based IM service, which enables you to combine your AIM, ICQ, Yahoo or MSN instant message accounts in one place.

Meebo wasn't first to offer Web-based instant messaging - but it is, by most accounts, the most efficient and easiest.

It isn't the ability to consolidate accounts that gets users excited, according to Sternberg and Wherry, who I met with recently, but simply the fact that meebo works as well on the Web as an IM software client works on your PC. Now you can be in touch with your IM buddies from any computer.

Wednesday's innovation is to take that capability and insert it into any page on the Internet, private or commercial. Once your Web site has a meebo window, when you log into meebo you not only see your usual buddies. You also can see a special group on your buddy list that represents visitors to your Web page.

"This is going to be really big with the MySpace kids," says Sternberg. I think he's right. After you've displayed yourself to the world in all your tasteless glory, won't you want to find out who's looking at it all? (I'm assuming you're 18.) Won't you want to have the capability to talk to them?

But meebo could be used as readily on eBay or Fortune.com, or IBM.com for that matter. The company will let any site use its service, with the only caveat that past a certain level of usage they might ask you to pay something. Otherwise it's free.

To use this meebo capability, just go to its homepage and get an account. Then download the code for the meebo "widget" and insert it into your Web page.

The earnestness and enthusiasm of meebo's founders is as endearing as the simplicity and apparent usefulness of its service. In a reversal of the usual pattern, the top technologists are the two women. Sternberg is the front man and marketing guy.

The company's ethos is resolutely informal and silly. The founders' actual names don't even appear on the site. Identified only by their first names, the founders are listed as "Biz Guy," (Sternberg) "Server Chick" (Jen), and "AJAX Girl" (Wherry). (Ajax is a software technology for creating interactive web pages, which Wherry uses for creating the meebo user interface.)

But meebo's software code, by all appearances, is rock solid and serious. It's backers are serious, too. Sequoia Capital, the venture capital firm that backed YouTube, invested in January. Netscape co-founder Marc Andreessen is an investor and advisor.

meebo, founded in September 2005, already has 700,000 user logins per day, up 60,000 in the three weeks since I met with the founders. Each user stays on the service an average of 69 minutes. That's a lot of time to show advertisements, which meebo will almost certainly eventually do.

Sternberg and Wherry say there will be plenty of ways to make money from meebo, but in classic old-school Web fashion that hasn't been their focus just yet. They expect, aside from traffic-based charges for heavy users, to make money with subtle targeted ads as well as by charging for personalization features.

We may be more than a decade into the Web, but it's still a pleasure to find a tiny 12-person company with a great product, enthusiastic founders and the potential to change the world.